• Preheat oven to 350 degrees.
• Grease the bottom and sides of an 8x8 square baking dish or pan.
• Peel, quarter and slice the apples thin.
• To keep the apples from browning while you prepare the batter, submerge the slices in plain cold water with a paper towel on top, or toss them in a little lemon juice. Set aside in the refrigerator until you're ready to assemble the cake.
• Cream the butter and sugar together until light and fluffy.
• Add the beaten egg, mixing well to incorporate.
• Add the vanilla.
• Sift or whisk together the flour, baking powder and salt.
• Add the dry ingredients and milk alternately to the butter mixture, mixing after each addition. Do not overmix.
• Assemble
• Mix together the cinnamon and powdered sugar and set aside.
• Spread the apples in a single overlapping layer on the bottom of the baking dish.
• Sprinkle with the mixture of cinnamon and sugar, and add another layer of apples and the remaining cinnamon and sugar.
• Pour the cake batter over the apples. The batter is rather thick and may need to be smoothed on top with a spatula or knife.

Bake

• Bake for approximately 25-30 minutes, or until a cake tester inserted into the center comes out clean.
• Remove cake from the oven and cool on a wire rack for about 15 minutes.

Serve

• Loosen the sides of the cake, turn it out carefully, upside down onto your serving plate; the top will be covered with a neat layer of transparent apples.
• Sprinkle the top with a little cinnamon sugar if desired.
• Serve warm with hard sauce or whipped cream.